Oxygen evolution reaction on MoS2/C rods—robust and highly active electrocatalyst

Abstract

Recently, water oxidation or oxygen evolution reaction (OER) in electrocatalysis has attracted huge attention due to its prime role in water splitting, rechargeable metal–air batteries, and fuel cells. Here, we demonstrate a facile and scalable fabrication method of a rod-like structure composed of molybdenum disulfide and carbon (MoS2/C) from parent 2D MoS2. This novel composite, induced via the chemical vapor deposition (CVD) process, exhibits superior oxygen evolution performance (overpotential = 132 mV at 10 mA cm−2 and Tafel slope = 55.6 mV dec−1) in an alkaline medium. Additionally, stability tests of the obtained structures at 10 mA cm−2 during 10 h followed by 20 mA cm−2 during 5 h and 50 mA cm−2 during 2.5 h have been performed and clearly prove that MoS2/C can be successfully used as robust noble-metal-free electrocatalysts. The promoted activity of the rods is ascribed to the abundance of active surface (ECSA) of the catalyst induced due to the curvature effect during the reshaping of the composite from 2D precursor (MoS2) in the CVD process. Moreover, the presence of Fe species contributes to the observed excellent OER performance. FeOOH, Fe2O3, and Fe3O4 are known to possess favorable electrocatalytic properties, including high catalytic activity and stability, which facilitate the electrocatalytic reaction. Additionally, Fe-based species like Fe7C3 and FeMo2S5 offer synergistic effects with MoS2, leading to improved catalytic activity and durability due to their unique electronic structure and surface properties. Additionally, turnover frequency (TOF) (58 1/s at the current density of 10 mA cm−2), as a direct indicator of intrinsic activity, indicates the efficiency of this catalyst in OER. Based on ex situ analyzes (XPS, XRD, Raman) of the electrocatalyst the possible reaction mechanism is explored and discussed in great detail showing that MoS2, carbon, and iron oxide are the main active species of the reaction.